There is a need to quickly measure the amounts of volatile species (hereinafter referred to as an analyte or analytes) dissolved in a liquid. Some examples include the measurement of dissolved carbon dioxide in water, beer, soda, wines, blood, and natural bodies of water such as in lakes, streams and marine systems. Other examples include measurement of flavors, ammonia, alcohol, etc. in various aqueous systems, or simply to measure vapor pressures of pure liquids.
One type of prior art device used to measure the amount of alcohol in liquids uses a sensor probe that is submersed in the liquid to be tested and includes a permeable membrane that allows the volatile alcohol to permeate through while blocking the water. The gaseous alcohol that permeates through the membrane is carried by a gas carrier in a measurement gas space through pairs of infrared sensors in a continuous flow. The sensors measure the concentration of alcohol in the liquid. This type of device is shown and explained in U.S. Pat. No. 6,834,536, entitled “Probe for Measuring Alcohol in Liquids”, issued 28 Dec. 2004.
By definition, (Ref. pp. 17-14, Perry's Handbook of Chemical Engineers, 6th ed., R. H. Perry and D. Green (eds)., 1984, McGraw Hill) molecules of the volatile substance have to first dissolve in the membrane on the liquid-side, then diffuse through the membrane, and desorb into the gas phase where the sensor is located. Such a permeation process can be agonizingly slow, and may be affected by the presence of other components present in solution.
The gas carrier must be provided for the device to operate with a reasonably small time constant, in which case, the small amounts of alcohol permeating will be diluted significantly making it harder for accurate sensing. This type of device is specifically designed for liquids with high alcohol concentrations that cannot be accurately measured with solid-state detectors. Further, because of the type of membrane used and the size of the measurement gas space, only high alcohol concentrations can be measured.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide new and improved analyzer apparatus for measuring the amounts of dissolved volatile substances in a liquid.
It is another object of the present invention to provide a new and improved method for measuring the amounts of dissolved volatile substances in a liquid.